The present invention relates to a method for converting haloacylaryl terminated organosiloxanes to the corresponding carboxyaryl terminated organosiloxanes by employing an aqueous mixture of an organic solvent, such as acetone.
Prior to the present invention, 4,4'-(1,1,3,3-tetramethyl-1,3-disiloxanediyl) bis(benzoic acid) having the formula, ##STR1## was made by the transition metal oxidation of the corresponding 1,3 alkylphenyl terminated tetramethyldisiloxane, or the caustic hydrolysis of the corresponding cyanophenyl terminated tetramethyldisiloxane. Tetramethyldisiloxane bis(benzoic acid) of formula (1) can be used in the preparation of a variety of liquid crystalline silicone polyesters as shown in copending application Ser. No. 319,028, filed Mar. 2, 1989.
As shown by Rich, U.S. Pat. No. 4,709,054, which is incorporated herein by reference, the intermediate 2-chlorodimethylsilylbenzoylchloride and 3-chlorodimethylsilylbenzoylchloride can be made by effecting reaction between isophthaloylchloride or terephthaloyl chloride and a chloropolymethylsilane, such as 1,1,2,2-tetradimethyldichlorodisilane in the presence of a transition metal catalyst. Rich by U.S. Pat. Nos. 4,604,442 and 4,604,477, which are incorporated herein by reference, shows that the corresponding tetramethyldisiloxane- bis(benzoyl chloride) can be made by hydrolyzing one of the aforementioned chlorodimethylsilylbenzoylchlorides. However, attempts to hydrolyze the aforementioned tetramethyldisiloxane bis(benzoyl chloride) to produce the corresponding diacid of formula (1) by standard means leads to decomposition of the starting material For example, treatment of tetramethyldisiloxane bis(benzoyl chloride) with either a 2% aqueous sodium hydroxide solution, or saturated sodium bicarbonate solution, results in the production of significant amounts of the corresponding cleavage product of the formula, ##STR2##